Session 4: Object-Oriented Programming and Arrays

1. Session 4: Object-Oriented Programming and Arrays iNET Academy Open Source Web Development

2. Objectives • Discuss object-oriented programming • Create Classes • Define methods • Inheritance • Discuss Arrays • Create arrays • Multidimensional arrays • Extract variables from arrays • Array functions in PHP

3. Object-oriented programming • Reuse code easier • Class • Attributes (Variables) • Methods (Functions) • Objects are instances created from a class

4. Creating a Class and an Instance • cat: a class • $fluffy: an instance of cat

5. Methods and Constructors • Methods are the functions defined within the class • Constructors are special methods which is called when a new instance of a class is created. Constructors is used to initialize class’s attributes. • Constructor may have parameters.

6. Defining Methods & Instantiating new Instance • Constructor returns reference to the object. This reference can be assigned to a variable • The parentheses () is optional when the constructor has no parameter

7. Variable Scope within Classes • Variable can have 3 scopes: • public: accessible from anywhere • private: accessible within the class • protected: acessible within subclass

8. Inheritance • Subclass inherit attributes and methods from parent class (superclass) • Use extend keyword to declare a subclass

9. The parent operator • To call parent class’s methods from subclass use parent::method_from_parent

10. Static Methods and Variables • Methods and Variables can be defined as static • Use :: operator to refer to static variables and static methods

11. Variable Reference • Use & operator to refer to the memory location of the variable • Using reference, we can have two variables refer to the same value

12. Array Fundametals • Two new terms: elements and indexes • Elements: the values stored in the array. • Each element is refered by an index • Index value can be a number or a string, but must be unique • Associative vs. Numeric Indexed Arrays • Numeric arrays use numbers as indexes. First element start at zero • Associative arrays use strings as indexes. Can be used to store configuration data since their keys have meaningful name.

13. Array Assignment • Via array identifiers • PHP does not report an error, but you can go through the array values sequentially

14. Array Assignment (cont.) • Using array function

15. Is_array function • Used to check whether a variable is an array

16. Referencing array values • Accessing array values using the form $array_name[index] • Associative arrays referenced in a string must be enclosed in curly braces {}

17. Looping through array values • Use foreach loop which automatically advances and reads each value from the array until it reaches the last value.

18. Adding values to an array • To add values to the end of array, use the array identifier • To add values the an associative array, use similar syntax

19. Counting elements in an array • Use count function or sizeof function

20. Sorting arrays • Use the sort() function • Elements are arranged from lowest to highest • Numbers are sorted numerically • String are sorted alphabetically • All previous key are removed, new keys are assigned. • Use asort() function to sort associative array and maintain index association

21. Multidimensional Arrays • Multidimensional arrays have other arrays as elements • Each set of keys and values represents a dimension

22. Display Multidimensional Arrays • Use var_dump() function

23. Extracting Variables from an Array • Use extract() function to place elements of an array into variables having the same names as the keys

24. Building an Array from Variables

25. Practice • In this practice, you will • Define a class named StaffInfo with the following attributes • ID • Name • DateOfBirth • Gender • Address • Telephone • Email • Use an array to store 10 objects typed StaffInfo. • Print the array in a table; same attributes are presented in a column.